gossipd: check consistency.

This is a hack to check that our gossip state is consistent on every
insert and delete.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

gossipd/broadcast.c

@@ -1,5 +1,14 @@
+#include <bitcoin/block.h>
+#include <bitcoin/pubkey.h>
+#include <bitcoin/short_channel_id.h>
+#include <ccan/crypto/siphash24/siphash24.h>
+#include <ccan/htable/htable_type.h>
 #include <ccan/mem/mem.h>
+#include <common/pseudorand.h>
+#include <common/status.h>
+#include <common/type_to_string.h>
 #include <gossipd/broadcast.h>
+#include <wire/gen_peer_wire.h>
 
 struct queued_message {
 	/* Broadcast index. */
@@ -25,6 +34,7 @@ void broadcast_del(struct broadcast_state *bstate, u64 index, const u8 *payload)
 {
 	const struct queued_message *q = uintmap_del(&bstate->broadcasts, index);
 	assert(q->payload == payload);
+	broadcast_state_check(bstate, "broadcast_del");
 }
 
 static void destroy_queued_message(struct queued_message *msg,
@@ -55,6 +65,7 @@ u64 insert_broadcast(struct broadcast_state *bstate,
 	/* Free payload, free index. */
 	new_queued_message(payload, bstate, payload, timestamp,
 			   bstate->next_index);
+	broadcast_state_check(bstate, "insert_broadcast");
 	return bstate->next_index++;
 }
 
@@ -71,3 +82,88 @@ const u8 *next_broadcast(struct broadcast_state *bstate,
 	}
 	return NULL;
 }
+
+static const struct pubkey *
+pubkey_keyof(const struct pubkey *pk)
+{
+	return pk;
+}
+
+static size_t pubkey_hash(const struct pubkey *id)
+{
+	return siphash24(siphash_seed(), id, sizeof(*id));
+}
+
+HTABLE_DEFINE_TYPE(struct pubkey,
+		   pubkey_keyof,
+		   pubkey_hash,
+		   pubkey_eq,
+		   pubkey_set);
+
+static void *corrupt(const char *abortstr, const char *problem,
+		     const struct short_channel_id *scid,
+		     const struct pubkey *node_id)
+{
+	status_broken("Gossip corrupt %s %s: %s",
+		      problem, abortstr ? abortstr : "",
+		      scid ? type_to_string(tmpctx,
+					    struct short_channel_id,
+					    scid)
+		      : type_to_string(tmpctx, struct pubkey, node_id));
+	if (abortstr)
+		abort();
+	return NULL;
+}
+
+struct broadcast_state *broadcast_state_check(struct broadcast_state *b,
+					      const char *abortstr)
+{
+	secp256k1_ecdsa_signature sig;
+	const u8 *msg;
+	u8 *features, *addresses, color[3], alias[32];
+	struct bitcoin_blkid chain_hash;
+	struct short_channel_id scid;
+	struct pubkey node_id_1,  node_id_2, bitcoin_key;
+	u32 timestamp, fees;
+	u16 flags, expiry;
+	u64 index = 0, htlc_minimum_msat;
+	struct pubkey_set pubkeys;
+	/* We actually only need a set, not a map. */
+	UINTMAP(u64 *) channels;
+
+	pubkey_set_init(&pubkeys);
+	uintmap_init(&channels);
+
+	while ((msg = next_broadcast(b, 0, UINT32_MAX, &index)) != NULL) {
+		if (fromwire_channel_announcement(tmpctx, msg, &sig, &sig, &sig,
+						  &sig, &features, &chain_hash,
+						  &scid, &node_id_1, &node_id_2,
+						  &bitcoin_key, &bitcoin_key)) {
+			if (!uintmap_add(&channels, scid.u64, &index))
+				return corrupt(abortstr, "announced twice",
+					       &scid, NULL);
+			pubkey_set_add(&pubkeys, &node_id_1);
+			pubkey_set_add(&pubkeys, &node_id_2);
+		} else if (fromwire_channel_update(msg, &sig, &chain_hash,
+						   &scid, &timestamp, &flags,
+						   &expiry, &htlc_minimum_msat,
+						   &fees, &fees)) {
+			if (!uintmap_get(&channels, scid.u64))
+				return corrupt(abortstr,
+					       "updated before announce",
+					       &scid, NULL);
+		} else if (fromwire_node_announcement(tmpctx, msg,
+						      &sig, &features,
+						      &timestamp,
+						      &node_id_1, color, alias,
+						      &addresses))
+			if (!uintmap_get(&channels, scid.u64))
+				return corrupt(abortstr,
+					       "node announced before channel",
+					       NULL, &node_id_1);
+	}
+
+	pubkey_set_clear(&pubkeys);
+	uintmap_clear(&channels);
+	return b;
+}

gossipd/broadcast.h

@@ -29,4 +29,9 @@ void broadcast_del(struct broadcast_state *bstate, u64 index, const u8 *payload)
 const u8 *next_broadcast(struct broadcast_state *bstate,
 			 u32 timestamp_min, u32 timestamp_max,
 			 u64 *last_index);
+
+/* Returns b if all OK, otherwise aborts if abortstr non-NULL, otherwise returns
+ * NULL. */
+struct broadcast_state *broadcast_state_check(struct broadcast_state *b,
+					      const char *abortstr);
 #endif /* LIGHTNING_GOSSIPD_BROADCAST_H */